Nonburning, nondripping, char-forming, polypropylene composition

Abstract

A nonburning, nondripping, char-forming composition of polypropylene by incorporating at least one of the following systems: 1. ammonium polyphosphate (preferably coated with stearylamine) and dipentaerythritol 2. melamine pyrophosphate and dipentaerythritol 3. reaction product of phosphoric acid, urea, dipentaerythritol, and melamine 4. reaction product of phosphoric acid, phosphorus pentoxide, at least one of pentaerythritol, dipentaerythritol, and tripentaerythritol; and melamine. Preferably all additive systems are degassed at elevated temperature to permit polypropylene compositions containing said additives to be molded without formation of voids. The thermal degassing of the phosphorus-containing flame retardant additive system prior to their incorporation with polypropylene considerably diminishes void formation or foaming during molding operation.

I claim: 
     
       1. A flame retarded, nonburning, nondripping, char-forming composition of polypropylene containing a flame retarding amount of a mixture of ammonium polyphosphate and dipentaerythritol where every 100 parts of polypropylene contain about 10 to 70 parts ammonium polyphosphate and about 5 to 30 parts dipentaerythritol with the total amount of the two additives being between about 30 and 90 parts. 
     
     
       2. The composition of claim 1 wherein the ammonium polyphosphate has been coated with about 1 to 3 weight percent stearyl amine. 
     
     
       3. The composition of claim 1 wherein every 100 parts of polypropylene contain 1 to 10 parts of fillers selected from a group consisting of glass fiber, titanium dioxide, or asbestos. 
     
     
       4. The composition of claim 1 wherein every 100 parts of polypropylene contain about 20 to 40 parts ammonium polyphosphate and about 10 to 20 parts dipentaerythritol with the total amount of the two additives being between about 40 and 60 parts. 
     
     
       5. The composition of claim 4 wherein the ammonium polyphosphate has been coated with about 1 to 3 weight percent stearyl amine. 
     
     
       6. The composition of claim 4 wherein the ammonium polyphosphate and dipentaerythritol are employed in a weight ratio of between 6:1 and 1:1. 
     
     
       7. A composition of claim 6 wherein the ammonium polyphosphate has been coated with about 1 to 3 weight percent stearyl amine. 
     
     
       8. The composition of claim 6 wherein every 100 parts of polypropylene contains about 1 to 10 parts of filler selected from a group consisting of glass fiber, titanium dioxide, or asbestos. 
     
     
       9. The composition of claim 1 wherein the combination of additives are thermally degassed prior to being used to formulate the polypropylene composition. 
     
     
       10. A flame retarded, nonburning, nondripping, char-forming composition of polypropylene containing a flame retarding amount of a composition resulting from the degassing of a mixture of ammonium polyphosphate and dipentaerythritol.